Many suction devices are known for moving many different materials into and along a suction passage. One type of such devices which is particularly pertinent to the preferred embodiments of the present invention is for surgery. With these devices, body fluids such as blood,and tissue are sucked away from surgical sites both to remove the material itself, for example a tumor, and to keep the site clear.
The material to be sucked along the passage of these devices in some uses, including surgery, is insufficiently fluid to flow well along the passage, and in surgery, in addition, blood, although normally fluid, naturally coagulates upon removal from the body and contact with foreign matter such as the suction passage to further tend to clog the apparatus. In surgery, therefore, fragments of the body tissue and coagulated blood often clog known suction apparatus. The time and effort for cleaning or replacing the apparatus to maintain its operability is always undesirable and, in surgery, can be critically detrimental.
One way of reducing the clogging of suction devices which is sometimes used in their surgical application is to irrigate the material to be aspirated before it enters the suction device. The combination of the material and the irrigation fluid is then sucked into the device where the irrigation fluid facilitates the movement of the material along the suction passage. Another way of avoiding the clogging problem which is also used in surgical applications to the extent practical, is to increase the cross-section of the passage. In surgical applications, however, the extent to which the cross-section can be enlarged is limited in order to limit the overall cross-section of the apparatus to a practical size. The irrigation of the tissue prior to aspiration also must be limited in surgery to avoid flooding the tissue site and to avoid squirting the irrigation fluid in an attempt at providing the volume of irrigation fluid required to prevent clogging of the suction passage. Even when both the volume of irrigation fluid and cross-section of the suction passage are maximized, the suction passage in surgical suction devices still tends to clog excessively.
Another way of avoiding clogging in some medical devices such as heart-lung machines is to introduce an anti-coagulant such as heparin into the blood. The resulting reduced coagulation of the blood then allows the device to operate without clogging. Such anti-coagulants cannot be introduced into an irrigation fluid for surgical operations, however, because the anti-coagulant will undesirably increase bleeding at the site and impair surgical control of bleeding and may damage the normal function of other tissues.